Through-flow spark arrester



Oct. 29, 1968 J. KRIZMAN THROUGH-FLOW SPARK ARRESTER Original Filed Dec. 27, 1965 l'm/ewroe. (Jo /v K/Z/ZMQNA WM,%Z w7,/Zm//w'a firroeA/Es s.

United States Patent THROUGH-FLOW SPARK ARRESTER John Krizrnan, 10549 Monogram Ave., 7 Granada Hills, Calif. 91344 Continuation of application Ser. No. 516,627, Dec. 27, 1965. This application Dec. 8, 1967, Ser. No. 697,543 6 Claims. (Cl. 55448) ABSTRACT OF THE DISCLQSURE A through-flow spark arrester having an outer shell with an enlarged center section which is axially between inlet and outlet sections connected to it by conical portions. The inlet section has means to accelerate and whirl entering gases, and a tubular outlet extends through the center and outlet sections, providing a trap chamber between it and the outer shell.

Cross referenc to related application This application is a continuation of my application Ser. No. 516,627, filed Dec. 27, 1965 now abandoned.

Background of the invention Spark arresters for small internal combustion engines in vehicles, such as motorcycles or other trail vehicles, or in generators, used in proximity to forests, must conform to standards which establish minimum performance and maintenance requirements designed to minimize the risk from exhaust spark fires.

The performance of spark arresters is measured by arresting efficiency which is defined as the percent of carbon particles retained or destroyed by the spark arrester when tested under prescribed conditions in a standard apparatus. An arresting efiiciency of at least 80 percent is required for all flow rates from 10 percent of the rated minimum flow rate to the rated maximum flow rate. The rated maximum flow rate is defined as the maximum rate of flow at which the back pressure, i.e., the differential pressure from intake to discharge of the arrester, is one pound per square inch. The rated minimum flow rate is defined as ten times the lowest flow rate at which 80 percent arresting efliciency is obtained. The rated flow range of the arrester is the range of flow rates, in cubic feet per minute, between the rated maximum flow rate and the rated minimum flow rate. Upon determination of the rated flow range of a specific spark arrester, it may be applied in the system of an engine which has an exhaust flow rate within the rated flow range under operating conditions of maximum speed and power.

The drop in arresting efficiency with increase in back pressure is a characteristic of various proposed spark arresting devices which separate carbon particles contained in exhaust gases fed thereto, and in which the gaseous stream undergoes one or more drastic changes in direction of flow, for example, a change in direction of 90 degrees or more prior to discharge to the atmosphere. Such changes in direction of flow in themselves result in an increase in back pressure which adversely influences the arresting efliciency and counteracts the desired objective. In addition, the prior art devices utilizing such systems are limited in their application in that, unless considerations of size are disregarded, they are suitable for use only in very small displacement engines, generally up to about cubic inches.

Further, other types and structures of spark arresters and other separator devices have been known, but these too have not been structures which perform at satisfactorily high arresting efficiencies, while having a minimal increase in back pressure. Some of these devices, for example, provide a structure which causes a re-circulation of gases, usually through a type of trap chamber. Such devices also have the effect of decreasing the arresting efiiciency while at the same time increasing back pressure.

In other instances, the prior art has provided highly complex and expensive devices which would be unsatisfactory for the present purposes.

Summary of the invention The present invention provides a through-flow spark arrester having three main components. The first is an outer shell which has an enlarged center section, and in axial alignment therewith, inlet and outlet sections of relatively smaller diameter. The inlet and outlet sections are connected to the center section by truncated conical portions. Within the inlet section there is a second component, which is in the nature of a cone and cylinder structure positioned coaxially in the inlet section and terminating at the junction of that inlet section with the adjacent conical portion. This structure has fins which extend in th annular space between it and the inside wall of the inlet section, and are so positioned as to impart a whirling motion to the gases and particles passing through this inlet section. In addition, the arrester by virtue of the thus reduced cross sectional area of the inlet section causes the exhaust gases and carbon particles flowing through it to be accelerated to a velocity significantly higher than the entry velocity thereof. The third component is a tubular outlet positioned coaxially within the outer shell and having its entry end adjacent the plane which passes through the juncture of the expanding conical portion (which is near the inlet section) and the enlarged center section, the other conical portion and into the outlet section, being sealed relatively to the outlet section. This construction thereby provides a trap chamber between the tubular outlet and the outer shell which has an entrance only at the annular space surrounding the inlet of the tubular outlet; this trap chamber in normal operation has no outlet. Accordingly, the gases and carbon particles are initially accelerated by the device in the inlet section, and are also caused to have a whirling motion. Immediately after leaving the inlet section, the cross sectional area of the gas passage through the spark arrester substantially increases, so that there is a reduction in the velocity of the gases; however, the carbon particles have substantial momentum due to the velocity imparted to the mass thereof and continue at a relatively high velocity generally ina direction outwardly of the axis of the arrester. They thereby enter into the trap chamber between the tubular outlet and the outer shell. During the initial operation, there is some entry of gas into this trap chamber, to the extent that the gas therein is compressed somewhat. Thereafter, there is no significant entry of gas into the trap chamber, but the gas is diverted into the tubular outlet, and thereby is caused to flow through the tubular outlet without a significant change in direction and without an increase in back pressure.

It is an object of this invention, therefore, to disclose and provide a spark arrester for internal combustion engines having a high arresting efficiency.

It is another object of this invention to disclose and provide a spark arrester including diffuser means for directing the flow of carbon particles contained in an exhaust gas outwardly to a carbon trap and the flow of the exhaust gas to an outlet tube for discharge to the atmosphere.

It is another object of this invention to disclose and provide a spark arrester having an extremely high arresting efficiency, through which an exhaust gas fed from an internal combustion engine travels substantially without changing direction of flow while being separated from carbon particles contained therein.

It is another object of this invention to disclose and provide a spark arrester for internal combustion engines having a displacement up to about 80 cubic inches and adapted to operate in a vertical, horizontal or inverted position.

It is a further object of this invention to disclose and provide a spark arrester which may be economically constructed and assembled and which requires a minimum of maintenance.

Other objects and advantages will be apparent from a reading of the following description and drawing.

Brief description of the drawing FIG. 1 is a longitudinal sectional view of the spark arrester of the present invention.

FIG. 2 is a transverse section taken along lines IH of FIG. 1.

FIG. 3 is a transverse section taken along lines Ill-J11 of FIG. 1.

FIG. 4 is a top View of the diffusing means shown in FIG. 1 taken along lines IVIV.

Description of the preferred embodiment Referring to FIG. 1, the spark arrester 16 of the present invention comprises a tubular outer shell having a relatively long center section 11. Center section 11 is positioned between the relatively short tubular inlet and outlet sections designated 13 and 14, respectively. The inlet section 13 and the outlet section 14 are of smaller diameter than the center section 11, and are in axial alignment with it. Joining and connecting the center section 11 and the inlet section 13 is an enlarging truncated conical portion 12, and similarly joining and connecting center section 11 with the outlet section 14 is a diminishing truncated conical portion 27. The terms enlarging and diminishing are with reference to the direction of flow through the spark arrester 10.

Within the inlet section 13 there is an accelerating and whirling means 15 comprising a centrally disposed cone portion 16 directed toward the inlet end of inlet section 13, the base of cone portion 16 being joined to a cylindrical portion 17, which has a relatively large diameter compared to the internal diameter of inlet section 13 and which thereby provides an annular space between the cylindrical portion 17 and the inlet section 13 which has a reduced cross sectional area in comparison to the cross sectional area of inlet section 13 in advance of the means 15. In the space between cylindrical portion 17 and inlet section 13 there are a plurality of circumferentially spaced path guiding fins 22, there preferably being six such fins spaced 60 degrees apart. These fins have substantially straight leading portions 23 and trailing portions angularly disposed to the longitudinal axis of the leading portion, to thereby form deflecting tabs 24. The fins 22 thereby cause gases and particles passing through the annular space to be whirled in a generally helical path. The fins 22 lie in planes which are angularly related to the longitudinal axis of the means 15, the leading portion 23 of each fin, for example, preferably being slanted to the radial centerline at an angle of 45 degrees, while the remainder of the fins slant gradually inwardly thereto to the trailing portion including the deflecting tab 24, which latter slants at an angle of about 15 degrees to the leading portion 23, as shown in FIGS. 2 and 3. To construct the means 15, the fin 22 may be joined to the cylindrical portion 17, as by soldering, and then the entire assemblage positioned within the inlet section 13 and soldered to the interior surface thereof.

It will be observed that the means 15 terminates adjacent the juncture between the inlet section 13 and the adjacent conical portion 12. At its other end, inlet section 13 has slots 28 to facilitate attachment to the exhaust pipe of an internal combustion engine.

A gas outlet from the spark arrester is provided by a tubular outlet 18 which is positioned within the outer shell. Tubular outlet 18 has an inlet end positioned adjacent the juncture of the enlarging conical portion 12 and the center section 11, and extends through the center section 11, the diminishing conical portion 27 and the outlet section 14. The tubular outlet 18 has a discharge end 19 which terminates at about the end of the outlet section 14. A portion of the outer surface of tubular outlet 18 is in substantial engaging contact with the inner surface of the outlet section 14, being held in assembled relation thereto, sealed against the escape of gases and carbon particles, by conventional means such as bolt 20 and nut 21. The outer shell comprising center section 11 and diminishing conical portion 27 thereby defines with tubular outlet 18 an annular space which may be seen in FIG. 1 to be closed at the juncture of conical portion 27 and outlet section 14. This annular space forms a carbon particle trap chamber 26 for the carbon particles 25.

In operation, hot exhaust gases containing carbon particles will be introduced into the inlet end of inlet section 13, at an average velocity determined primarily by the operating characteristics of the engine and the atmospheric pressure. The velocity of the gases and the carbon particles will remain substantially unchanged until they reach means 15, where they will begin to be accelerated to a higher velocity. In addition to being accelerated to a higher velocity, the gases and carbon particles will have a whirling motion imparted to them by the fins 22. As the gases and carbon particles leave the means 15, the cross sectional area of the passage rapidly increases due to the termination of means and the configuration of enlarging conical portion 12. Due to the mass and velocity of the carbon particles, they will have a momentum which will not be significantly affected by the enlarging cross sectional area of the passage and the consequent deceleration of the gases; accordingly, the gas particles will continue at relatively high velocity in a whirling and somewhat outwardly directed path, and will thereby enter the carbon particle trap chamber 26. The exhaust gases will initially tend to compress the gases already existing in the space between the tubular outlet 18 on the one hand and the center section 11 and diminishing conical portion 27 on the other hand. Therefore, these gases being somewhat compressed in an annular space which has only an entrance and a dead end, will not permit the flowing gases significantly to enter the annular space, but these flowing gases will pass without a substantial change in direction from the enlarging conical portion 12 into the tubular outlet 18, and thence through the discharge end 19 thereof.

The carbon particle 25 may be removed from carbon trap 26 by removing bolt and then removing the tubular outlet. Alternatively, the arrester may be provided with a suitable opening (not shown) covered by a closure such as a band during normal engine operation. The band may be removed, and the engine operated at a safe location, thereby permitting the engine exhaust to flush the carbon particles from the carbon particle trap chamber 26 and through the opening. To operate in a vertical position, the carbon trap may be extended longitudinally beyond the cylindrical portion of the diffusing means in the direction of the cone portion so that it surrounds the inlet tube beyond the area where the fins are positioned, and a clean-out opening provided in the shell body in the area adjacent to such extension for removal of the carbon particles.

The present invention provides a very compact spark arrester made of a few simple parts, and having a very high spark arresting efliciency without a significant increase in back pressure, or other factor which would interfere with the efiicient operation of the engine to which it is attached.

It is to be understood that various modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.

I claim:

1. A through-flow spark arrester for an internal combustion engine comprising:

a tubular outer shell comprising a center section positioned between inlet and outlet sections, said inlet and outlet sections being of smaller diameter than said center section, in axial alignment therewith, and joined thereto by truncated conical portions, which respectively enlarged and diminish in the direction of flow, said center section being relatively long and said inlet and outlet sections being relatively short;

means centrally disposed within said inlet section for reducing the cross sectional area thereof and causing the gases and particles flowing therethrough to achieve an increased'velocity and a whirling motion, whereby said particles have imparted to them a force urging them away from the axis of said arrester, said means terminating adjacent the juncture of said inlet section and the adjacent conical portion, said means including a plurality of circumferentially spaced fins lying in planes angularly related to the radial center line of said means;

and a gas outlet from said arrester comprising a tubular outlet within said outer shell having an inlet end adjacent the juncture of said enlarging conical portion and said outer shell center section and extending within said outer shell, said diminishing conical portion and said outlet section, a portion of the outer surface of said tubular outlet engaging the inner surface of said outlet section, said outer shell and tubular outlet defining an annular space closed at the juncture of said diminishing conical portion and said outlet section, said tubular outlet constituting the sole outlet from said arrester during normal operation thereof;

whereby combustion gases containing solid particles entering said inlet section are accelerated and whirled, the gases then decelerating in the enlarging conical section, enabling the particles to be carried by their momentum through said conical portion and into said annular space, the gases entering the inlet end of the tubular outlet without substantial change of direction and thence passing from said arrester.

2. A spark arrester as defined in claim 1 wherein each of said fins includes a leading portion and a trailing portion, said trailing portion including a deflecting tab disposed in angular relatonship to the longitudinal axis of said leading portion.

3. A spark arrester as defined in claim 2 wherein the leading portion of the fin is slanted to the longitudinal axis of said means at an angle of about degrees and the deflecting tab is slanted at an angle of about 15 degrees.

4. A spark arrester as defined in claim 2 wherein the defleeting tab is disposed at an angle of about 15 degrees to the longitudinal axis of the leading portion.

5. A spark arrester as defined in claim 1, wherein the said fins are spaced apart about degrees.

6. A spark arrester as defined in claim 1, and including releasable means for holding said tubular outlet in said position in said outlet section, whereby said tubular outlet may be readily removed from said outer shell.

References Cited UNITED STATES PATENTS 588,096 8/ 1897 Swartzbaugh. 1,215,935 2/1917 Hickman. 2,004,468 6/ 1935 Hawley. 2,569,909 10/ 1 Omney. 2,646,854 7/1953 Walker. 2,659,450 11/ 1953 Baird. 2,662,610 12/ 1953 Heinrich. 2,866,518 12/ 1958 Lincoln. 3,009,539 11/1961 Papp. 3,064,41 1 1 l/ 1962 Breslove. 3,216,182 11/1965 Cochran et al.

FOREIGN PATENTS 1,106,384 7/1955 France.

HARRY B. THORNTON, Primary Examiner. B. NOZICK, Assistant Examiner. 

